title: A thraustochytrid diacylglycerol acyltransferase 2 with broad substrate specificity strongly increases oleic acid content in engineered Arabidopsis thaliana seeds.
abstract: Diacylglycerol acyltransferase (DGAT) catalyses the last step in acyl-CoA-dependent triacylglycerol (TAG) biosynthesis and is an important determinant of cellular oil content and quality. In this study, a gene, designated TaDGAT2, encoding a type 2 DGAT (DGAT2)-related enzyme was identified from the oleaginous marine protist Thraustochytrium aureum. The deduced TaDGAT2 sequence contains a ~460 amino acid domain most closely related to DGAT2s from Dictyostelium sp. (45-50% identity). Recombinant TaDGAT2 restored TAG biosynthesis to the Saccharomyces cerevisiae H1246 TAG-deficient mutant, and microsomes from the complemented mutant displayed DGAT activity with C16 and C18 saturated and unsaturated fatty acyl-CoA and diacylglycerol substrates. To examine its biotechnological potential, TaDGAT2 was expressed under control of a strong seed-specific promoter in wild-type Arabidopsis thaliana and the high linoleic acid fad3fae1 mutant. In both backgrounds, little change was detected in seed oil content, but a striking increase in oleic acid content of seeds was observed. This increase was greatest in fad3fae1 seeds, where relative amounts of oleic acid increased nearly 2-fold to >50% of total fatty acids. In addition, >2-fold increase in oleic acid levels was detected in the triacylglycerol sn-2 position and in the major seed phospholipid phosphatidylcholine. These results suggest that increased seed oleic acid content mediated by TaDGAT2 is influenced in part by the fatty acid composition of host cells and occurs not by enhancing oleic acid content at the TAG sn-3 position directly but by increasing total oleic acid levels in seeds, presumably by limiting flux through phosphatidylcholine-based desaturation reactions.
authors.affiliation: National Key Lab of Crop Genetic Improvement and College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Chunyu
authors.initials: C
authors.lastname: Zhang
authors.forename: Umidjon
authors.initials: U
authors.lastname: Iskandarov
authors.forename: Elliott T
authors.initials: ET
authors.lastname: Klotz
authors.forename: Robyn L
authors.initials: RL
authors.lastname: Stevens
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Cahoon
authors.forename: Tara J
authors.initials: TJ
authors.lastname: Nazarenus
authors.forename: Suzette L
authors.initials: SL
authors.lastname: Pereira
authors.forename: Edgar B
authors.initials: EB
authors.lastname: Cahoon
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D051048:Diacylglycerol O-Acyltransferase / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D019301:Oleic Acid / Q000378:metabolism*; D010802:Phylogeny; D012639:Seeds / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D019301:Oleic Acid; D051048:Diacylglycerol O-Acyltransferase
keywords: Arabidopsis; Thraustochytrium aureum; diacylglycerol acyltransferase; fatty acid; oilseed; oleic acid; triacylglycerol